Question

The strain energy stored in a spring when it is subjected to maximum load without suffering permanent distortion is known as

• A. impact energy
• B. proof resilience
• C. proof stress
• D. modulus of resilience

Hint:

Proof resilience deals with total energy, while modulus of resilience deals with energy per unit volume.

Answer 1

The Correct Option is B

Step 1: Understanding strain energy.
Strain energy is the energy stored in a body due to deformation caused by an applied load.
Step 2: Defining proof resilience.
Proof resilience is defined as the maximum strain energy that a body can store without undergoing permanent deformation, i.e., within the elastic limit.
Step 3: Eliminating incorrect options.
Impact energy refers to energy due to sudden loading.
Proof stress is the stress corresponding to a specified permanent strain.
Modulus of resilience is the proof resilience per unit volume.
Step 4: Conclusion.
Therefore, the strain energy stored without permanent distortion is called proof resilience.

Answer 2

The question is asking for the specific term used for the strain energy a body absorbs when loaded up to its elastic limit, just short of permanent set. Let's examine what each listed quantity actually represents:

1. Impact energy: This describes the kinetic energy delivered to a component during a sudden or shock load, such as a falling weight striking a spring or beam. It describes how the energy is applied, not a measure of how much elastic strain energy the material itself can safely store, so it does not match the definition given.
2. Proof resilience: This is defined precisely as the maximum energy that can be stored in a body when loaded within its elastic range, i.e. up to the point where any further loading would cause permanent (plastic) deformation. Since the question describes "maximum load without suffering permanent distortion," this matches the definition word for word.
3. Proof stress: This is a stress value, not an energy quantity, used for materials that do not show a sharp yield point; it is the stress producing a small specified permanent strain (commonly 0.2%). Because the question asks for an energy quantity, this option is not conceptually appropriate.
4. Modulus of resilience: This is closely related but is the proof resilience expressed per unit volume of material, i.e. an energy density rather than a total stored energy. Since the question does not mention "per unit volume," this is a distinct, more specific quantity than what is being asked for.

Only proof resilience refers to the total elastic strain energy a body can absorb without permanent distortion, matching the question exactly.

Therefore, the correct answer is proof resilience.